Thermal time delay



Jan. 11, 1966 A. F. DEMING 3,229,169

THERMAL TIME DELAY Filed June 26, 1961 INVENTOR.

ANDREW F. DEM/N6 W 4 I M United States Patent 7 3,229,169 THERMAL TIME DELAY Andrew F. Deming, Alliance, Ohio, assi'gnor to Consolidated Electronics Industries Corp'., a corporation of Delaware v I Filed June 26, 1961, Ser. No. 119,620 14 Claims. (Cl. 317-147) The invention relates in general to time delay circuits and, more particularly, to radio circuits incorporating a thermal time delay to avoid response to spurious energy. I Many radio circuits have need for some form of time delay in various portions of the circuit and one such use is to avoid response to spurious energy, such as that contained in lightning, which otherwise might trigger the radio circuit to give a false signal. A more specific use for the invention described herein is in radio controlled garage door operators, wherein a carrier containing a lower frequency intelligence may be transmitted as a signal. This lower frequency intelligence may be in the form of modulation on the carrier wave or it may be in the form of an interrupted carrier wave at a specified rate,'for example a sub-audio frequency. This carrier wave with contained intelligence is broadcast, usually by'a short-range portable transmitter, to a receiver having circuits designed to receive this particular combination of carrier and intelligence component. Various carrier frequencies and various modulation frequencies permit many combinations to permit private operation for security. The receiver is tuned to the particular carrier frequency and has a detector to obtain the intelligence frequency. When the combination of carrier and intelligenoe frequency is correct, this signal is passed by the receiver to a pilot relay which is energized to control actuation of the garage door operator. Such systems have been used in the past but have been subject to spurious operation by random atmospheric disturbances and, more particularly, lightning'fiashes. The latter is an are discharge containing many random frequencies and, of course, at high amplitude. The energy received by the receiver from such lightning flashes is often sufficient to pass a certain portion at the frequency of the intelligence component to actuate the pilot relay.

7 Accordingly, an object of the invention is to provide a time delay so that random atmospheric disturbances, such as lightning, will not actuate the pilot relay of such a radio receiver.

Another object of the invention is to provide an electronic circuit for use with a signal voltage wherein a thermal time delay circuit is provided which includes a thermionic tube having an anode and a cathode including a filament. Output means is connected in circuit with the anode and cathode and a filament voltage source is connected to at least part of the filament to energize same at a value insufficient to raise the cathode to normal electron emission, and means is provided QOnllQG-ting at least part of the filament to be energized in accordance with the signal voltage whereby, after a time delay, the cathode is raised to substantially normal emission to cause conduction of the t rmionic t be.

rq i t t the i vention i to provide a thermal m ela seem n span t e thermal. lag in emission diar e er ssd a thei nn e tube.

Anotherobject of the invention is to provide a thermal time de a ii' ll l ill l'uding a first means to partially he??? d aihii fi and a second means to heat the cathode stil furtherto obtain normal emission after a time delay.

Another object of the invention is to provide a dual heat source for a thermionic tube filament with one heat source providing initial partial heating of the filament and the second source providing a time delay before heat.-

"ice

ing of the filament suflicie'nt to cause effective conduction of the thermionic tube.

Other objects and afuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

The single figure of the drawing shows a radio circuit incorporating the thermal time delay circuit of the in.- vention.

The drawing shows a thermal time delay circuit 11 as incorporated in part of a radio circuit 12. This radio circuit 12 may be in the form of a radio receiver receiving energy on an antenna 13 relative to ground 14. The radio receiver 12 may include the usual forms of amplification, amplifying the energy by amplifiers, not shown and supplied to a transformer 15. The radio receiver '12 may be, for purposes of example, one usuable with a remotely controlled garage door operator. A transmitter, not shown, transmits a carrier containing a low frequency intelligence, such as a low frequency modulation component, or a carrier interrupted at a lower frequency, such as a sub-audio frequency. This carrier and intelligence component is received on the antenna 13 and amplified, and appears at the transformer This transformer passes the carrier to a detector 18 which develops the intelligence component across a detector load resistor 19. This intelligence component is passed by a capacitor 20 to an amplifier 21 which, in turn, passes the amplified intelligence component or signal voltage to another amplifier 22. This amplifier has a cathode 23 and an anode 24 connected in circuit with a demodulator relay 25. This demodulator relay 25 is connected as a cathode follower in the circuit of the amplifier 22. The demodulator relay 25 has contacts 26 adapted to be closed when the demodulator relay 25 is energized, and is in the form of a tuned relay, so that the contacts 26 are actuated at the frequency of the intelligence component so long as this intelligence component received on the antenna 13 is the same as the frequency to which the relay 25 is tuned.

The radio circuit 12 includes a power transformer 30 energized from an alternating current source 31. A high voltage secondary 32 supplies a voltage through a rectifier 33 and a capacitor 34 to supply a direct current operating voltage on conductor 35. This supplies operating voltages for the amplifiers 21 and 22.

A thermionic tube 38 is provided with an anode 39 and a filamentary cathode 40. This filament 40 is in two sections connected in series at a midtap 41 which is internally connected to a suppressor grid 42. This therm ionic tube 33 is shown as a pentode, but with the control and screen grids both tied to the anode 39 so that this tube 38 acts as a diode. One end 42 of the filament 40 is connected to ground and the other end 43 is connected through a current dropping resistor 44 to a secondary 45 on the transformer 30, which acts as a filament "supply voltage source. This secondary 45 supplies the filament voltage to the amplifiers 21 and 22 which may he 63 volt filament tubes and, accordingly, the current dropping resistor 44 is used to lower the voltage and, hence,

current to the filament 40 to a value insufficient to establish effective conduction through the thermionic tube 38. The anode 39 is connected through a resistor 48 and a pilot relay winding 4% to the positive direct current operat- 7 ing voltage source on conductor 35. The pilot relay has contacts 50 which will be closed upon sufiicient energization of the pilot relay winding 49. A voltage dropping resistor 51 is connected from the end 43 of the filament 40 through the demodulator relay contacts 26 to the positive direct current source on conductor 35.

The thermionic tube 38 provides a thermal time delay in the order of to 1 second before pull-in of the pilot relay contacts 50. 'It has been found that a type 3V4 tube is satisfactory for the thermionic tube 38. This tube happens to be. a power pentode and in the particular application shown, it is connected as a diode. The 3V4 tube has two 1.4 volt sections of the filament connected in series for a 2.8 volt filament operation or, alternatively, the two sections may be connected in parallel for 1.4 volt operation. The midtap 41 has an external pin connection for this purpose. The current dropping resistor 44 drops the current through the filament 40 to about half normal current which heats the filament but does no raise it to the temperature of effective electron emission. However, when an incoming signal is received on the antenna 13, it is detected at the detector 18 and amplified and applied to the demodulator relay 25. If this intelligence component agrees with the frequency to which the relay is tuned, the contacts 26 will vibrate at that particular incoming frequency, e.g., 20 cycles. This periodic actuation of the contacts 26 applies an interrupted high volt age through the voltage dropping resistor 51 to the filamen 40. Assuming that the contacts 26 are closed 40% of the time, the impedance of the resistor 51 will be so selected in accordance with the voltage on conductor 35, so as to raise the filament temperature to approximately normal temperature for efiicient and normal electron emission. This takes a certain finite time, e.g., A of a second, and then the thermionic tube 38 conducts to cause pull-in of the pilot relay contacts 50. Thus, the time required to :heat the filament to achieve effective electron emission establishes a time delay period before actua-tion of the relay contacts 50.

This thermal time delay circuit has many applications and, in particular, it is useful in the circuit shown, wherein the radio receiver 12 is subject to receiving random or spurious interference such as energy from lightning. Such spurious interference often contains energy at very many frequencies and it is always possible that the energy re ceived might contain sufiicient energy at both the selected carrier and intelligence frequencies so that it will be passed to the demodulator relay 25 and actuate such demodulator relay contacts for one or two cycles. At the sub-audio frequency of intelligence given above as an example, namely, 20 cycles, it will take five periodic actuations of the demodulator relay contact 26 before sufficient additional heat has been imparted to the filament 40 to cause pull-in of the pilot relay contacts 50. This is assuming 4 of a second delay. The length of the time delay may 'be decreased by increasing the temperature of the filament 40 as determined by the filament supply source 45 and current dropping resistor 44. Alternatively, the voltage of the secondary voltage source 35 may be increased or the value of the voltage dropping resistor 51 may be decreased to apply an over-voltage on the filament 40 to rapidly bring the thermionic tube 38 to effective electron emission levels. In garage door operator service, the modulated carrier wave from a transmitter is generally transmitting for only a few seconds and, accordingly, any over-voltage applied to the filament 40 would only be for a few seconds so as not to be harmful. Of course, the time delay may be increased by decreasing the amount of continuous heat on the filament 40 or by decreasing the amount of additional heat supplied through the demodulator relay cont-acts 26, or by usingua cathode sleeve-type thermionic tube which will have an increased thermal lag.

'The secondary 45 is a first voltage source to at least.

partially energize the filament 40 or to apply a Voltage to at least part of this filament. The secondary 32 and rectifier 33 supplying a positive direct current voltage is a secondary voltage source to supply a voltage which at least partially energizes the filament 40 or to supply a voltage to at least a part of the filament 40. 'The first voltage source 45 and resistor 44 are insuflicient to establish normal electron emission from the filamentary cathode 40, and the second source'in combination with the first source, is sufii-cient to establish substantially normal electron emission. Accordingly, the invention shows the use of dual voltage sources applied selectively to obtain a thermal time delay circuit.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope .of the invention as hereinafter claimed.

What is claimed is:

1. In a radio receiver circuit for use with a carrier wave having a lower frequency intelligence thereon, a thermal time delay circuit including contact means actuated in accordance with said lower frequency intelligence, a thermionic tube having an anode and a cathode, output means connected in circuit with said anode and said cathode, first means including a first voltage to partially heat said cathode, and second means including a second voltage and responsive to said lower frequency intelligence to heat the cathode through said contact mean still further to obtain normal electron emission after a time delay.

2. In an electronic circuit for use with a signal voltage, a thermal time delay circuit including contact means actuated in accordance with said signal voltage, a thermionic tube having an anode and a cathode including a filament, output means connected in circuit with said anode and said cathode, a dual heat source for said cathode including a first heat source providing initial partial heating of said filament and a second source energizing said filament through said contact means and providing a time delay before heating of said filament sufiicient to cause effective conduction of said thermionic tube to energize said output means.

3. In a radio circuit for use with a signal voltage, the" provision of a thermal time delay circuit including contact means actuated in accordance with said signal voltage, a thermionic tube having an anode and a cathode including a filament, a filament voltage source and a second voltage source, output means connected in circuit with said anode and said cathode, means connecting at least part of said filament to said filament voltage source to energize said part at a value insufiicient to raise said cathode to normal electron emission, and means connecting at least part of said filament through said contact means to said second voltage source, whereby, when said contact means are periodically actuated at said signal voltage frequency, said cathode after a time delay is raised to substantially normal emission to cause conduction of said thermionic tube.

4. In a radio circuit for use with a signal voltage, the provision of a thermal time delay circuit including contact means actuated in accordance with said signal voltage, .a thermionic tube having an anode and a cathode including a filament, a pilot relay having a winding, a filament voltage source and a second voltage source, circuit means connecting said pilot relay winding in circuit with said anode and said cathode, means connecting at least part of said filament to said filament voltage source to energize said part at a value insufiicient to cause pull in of said pilot relay, and means connecting at least par-t of said filament through said contact means to said second; voltage source, whereby, when said contact means are actuated at said signal voltage frequency, said filament after a time delay is energized to a. value sufficientto causeconduction of said thermionic tube and pull in of said pilot relay.

5. In a receiver circuit for use with a carrier wave having a lower frequency intelligence thereon and subject to spurious interference energy, and demodulator means within said receiver circuit to obtain said lower frequency output, the provision of a thermal time delay circuit including a thermionic tube having "an anode and a cathode including a filament, a pilot relay having a winding, a filament voltage source, circuit means connecting said pilot relay winding in circuit with said anode and said cathode, means connecting at least part of said filament to said filament voltage source to energize said part at a value insuificient to cause pull in of said pilot relay and means connecting at least part of said filament to be energized in accordance with said lower frequency output of said demodulator, whereby, when said demodulator has said lower frequency output, said filament after a time delay is energized to a value sufficient to cause conduction of said thermionic tube and pull in of said pilot relay.

6. In a circuit for use with a carrier wave having a lower frequency intelligence thereon and subject to spurious interference, the provision of a thermal time delay circuit including contact means, means to actuate said contact means at said lower frequency rate and adapted to be actuated by energy from any said spurious interference, a thermionic tube having an anode and a cathode including a filament, a filament voltage source and a second voltage source, output means connected in circuit with said anode, and said cathode, means connecting at least part of said filament to said filament voltage source to energize said filament at a value insufiicient to raise said cathode to normal electron emission, and means connecting at least part of said filament through said contact means to said second voltage source, whereby, when said contact means are periodically actuated at said lower.

frequency, said cathode after a time delay is raised to substantially normal emission to cause conduction of said thermionic tube.

7. In a receiver circuitfor receiving a carrier wave having a lower frequency intelligencethereon and subject to receiving energy from lightning flashes within the frequencyof the said carrier wave, and demodulator means within said receiver circuit to obtain said lower frequency output, the provision of a thermal time delay circuit including contact means actuated by said demodulator meansat said lower frequency rate and adapted to be actuated by energy from any saidlightning flashes, a thermionic tube'having an anode and'a cathode including a filament, a pilot relay having a winding, a voltage source, circuit means-connectingsaidpilot relay winding in circuit with said anode and said cathode, and means connecting said filament. through said demodulator contact means to said voltage source, whereby, when said demodulator contact means are periodically actuated at said lower frequency, said voltage source energizes said filament after a time delay to a value of energization to cause conduction of said thermionic tube and pull in of said pilot relay.

3. In a receiver circuit for receiving a carrier wave having a lower frequency intelligence thereon and subject to receiving energy from lightning flashes within the frequency of the said carrier wave, and demodulator means within said receiver circuit to obtain said lower frequency output, the provision of a thermal time delay circuit including contact means actuated by said demodulator means at said lower frequency rate and adapted to be actuated by energy from any said lightning flashes, a thermionic tube having an anode and a cathode including a filament, a pilot erlay having a winding, a filament voltage source and a second voltage source, circuit means connecting said pilot relay winding in circuit with said anode and said cathode, means connecting at least part of said filament to said filament voltage source to energize said part at a value insufficient to cause pull in of said pilot relay, and means connecting at least part of said filament through said demodulator contact means to said second voltage source, whereby, when said demodulator contact means are periodically actuated at said lower frequency, said filament after a time delay is energized to a value sufficient to cause conduction of said thermionic tube and pull in of said pilot relay.

v 9. In a receiver circuit for receiving a carrier wave having allower frequency intelligence thereon and'subject to receiving energy from lightning flashes within the frequency of the said carrier wave, and demodulator means within said receiver circuit to obtain said lower frequency output, the provision of a thermal time delay circuit including contact means actuated'by said demodulator means at said lower frequency rate and adapted to be actuated'by energy from any. said lightning flashes, a thermionic tube having an anode and a cahode including a filament, a pilot relay having a winding, a filament voltage source and a second voltage source, circuit means connecting said pilot relay winding in circuit with said anode and said cathode, means connecting said filament to said filament voltage source to energize said filament ata value insufficient to cause pull in of saidvpilot relay, and means connecting said filament through said demodulator contact means to said second voltage source, whereby, when said demodulator contact means are-periodically actuated at said lower frequency, said second voltage source energizes said filament after a time delay, to a value of energization to cause conduction of said thermionic tube and pull in of said pilot relay.

7 1t). Inareceiver circuit for receiving a. carrier wave frequency output, the provision of a thermal timedelay.

circuit'including contact means actuated by said demodu lator means at said lower frequency rate and adapted to betactuatedby energy from any said lightning flashes, a thermionic tube having a filament and an anode, apilot relayihaving a winding, a filament voltage source, a second voltage source, means connecting said pilot relay winding between said anode and said second voltage source, means connecting said filament to said filament voltage source to energize said filament at a value insuflicient to cause conduction of said thermionic tube, and means connecting said filament through said demodulator contact means to saidsecond voltagesource, whereby, when said demodulator contact means are periodically. actuated at said lower frequency, said second voltage source energizes said filament to approximately full energization' after a time delay'to cause conduction of said. thermionic tube andpull in of said pilot relay.

11. In a receiver circuit for receiving a carrier wave having a lower frequency intelligence thereon and subject to receiving energy from lightning flashes within the frequency of the said carrier wave, and demodulator means within said receiver circuit to obtain said lower frequency output, the provision of a thermal time delay circuit including contact means actuated by said demodulator means at said lower frequency rate and adapted to be actuated by energy from any said lightning flashes, a thermionic tube having a filament and an anode, a pilot relay having a winding, a direct current supply source, means connecting said pilot relay winding between said anode and said direct current supply source, an alternating current filament supply voltage, means connecting said filament of said filament supply voltage to energize said filament at a value insuificient to cause conduction of said thermionic tube, and means connecting said filament through said demodulator contact means to said direct current supply source, whereby, when said demodulator contact means are periodically actuated at said lower frequency, said direct current supply source energizes said filament to approximately full energization after a time delay to cause conduction of said thermionic tube and pull in of said pilot relay.

12. In a receiver circuit for receiving a carrier wave having a lower frequency intelligence thereon and subject to receiving energy from lightning flashes within the frequency of the said carrier wave, and demodulator means within said. receiver circuit to obtain said lower frequency output, the provision of a thermal time delay circuit including contact means actuated by said demodulator means at said lower frequency rate and adapted to be actuated by energy from any said lightning flashes, a thermionic tube having a filamentary cathode and having an anode, a pilot relay having a winding, a direct current supply source, means connecting said pilot relay winding between said anode and said direct current supply source, one end of said filamentary cathode being connected to ground, an alternating current filament supply voltage, means connecting the other end of said filamentary cathode to said filament supply voltage to energize said filamentary cathode at a value insufficient to cause conduction of said thermionic tube, and a voltage dropping resistor connecting said other end of said filamentary cathode through said demodulator contact means to said direct current supply source, whereby, when said demodulator contact means are periodically actuated at said lower frequency, said direct current supply source energizes said filamentary cathode to approximately full energization after a time delay to cause conduction of said thermionic tube and pull in of said pilot relay.

13. In a receiver circuit for receiving an interrupted carrier wave and subject to receiving energy from lightning flashes within the frequency of the said carrier wave, demodulator means within said receiver circuit to obtain a sub-audio frequency output at the interruption rate, and contact means in said demodulator means actuated at said interruption rate and adapted to be actuated by energy from any said lightning flashes, a thermal time delay circuit including, the provision of a thermionic tube having a filamentary cathode and having an anode, a pilot relay having a winding, a direct current supply source, means connecting said pilot relay winding between said anode and said direct current supply source, one end of said filamentary cathode being connected to ground, an alternating current filament supply voltage, means connecting the other end of said filamentary cathode to said filament supply voltage to energize said filamentary cathode at approximately half rated current but insufficient to cause conduction of said thermionic tube, and a voltage dropping resistor connecting said other end of said filamentary cathode through said demodulator contact means to said direct current supply source, whereby, when said demodulator contact means are periodicallyactuated at said interruption frequency, said direct current supply source energizes said filamentary cathode to approximately full energization after a time delay to cause conduction of said thermionic tube and pull in of said pilot relay.

14. A thermal time delay circuit including a radio receiver circuit for receiving an interrupted carrier wave and subject to receiving energy from lightning flashes in the frequency of the said carrier wave, demodulator means within said receiver circuit to obtain a sub-audio frequency output at the interruption rate, contact means in said demodulator means actuated at said interruption rate and adapted to be actuated by energy from any said lightning flashes, a thermionic tube having a filamentary cathode and having an anode, a pilot relay having a winding, a direct current supply source, a current limiting resistor connecting said pilot relay winding between said anode and said direct current supply source, one end of said filamentary cathode being connected to ground, an alternating current filament supply voltage, a current dropping resistor connecting the other end of said filamentary cathode to said filament supply voltage to energize said filamentary cathode at approximately half rated current but insufficient to cause conduction of said thermionic tube, and a voltage dropping resistor connecting said other end of said filamentary cathode through said demodulator contact means to said direct current supply source, whereby, when said demodulator contact means are periodically actuated at said interruption frequency said direct current supply source energizes said filamentary cathode to approximately full energization after a time delay in the order of one-fourth to one second to cause conduction of said thermionic tube and pull in of said pilot relay.

References Cited by the Examiner UNITED STATES PATENTS 1,766,038 6/1930 Gebhard 32891 1,872,560 8/1932 Breisky 317142 2,055,921 9/1936 Baker 32827O 2,143,501 1/1939 Snyder 317142 2,318,948 5/1943 Koch 328-270 2,695,977 11/1954 Hupert et a1 317-142 2,923,862 2/1960 Teich 317-142 FOREIGN PATENTS 558,004 12/ 1943 Great Britain. 120,768 12/ 1945 Australia.

SAMUEL BERNSTEIN, Primary Examiner. 

1. IN A RADIO RECEIVER CIRCUIT FOR USE WITH A CARRIER WAVE HAVING A LOWER FREQUENCY INTELLIGENCE THEREON, A THERMAL TIME DELAY CIRCUIT INCLDUIGN CONTACT MEANS ACTUATED IN ACCORDANCE WITH SAID LOWER FREQUENCY INTELLIGENCE, A THERMIONIC TUBE HAVING AN ANODE AND A CATHODE, OUTPUT MEANS CONNECTED IN CIRCUIT WITH SAID ANODE AND SAID CATHODE, FIRST MEANS INCLUDING A FIRST VOLTAGE TO PARTIALLY HEAT SAID 